NFL cheerleaders have been entertaining crowds at football games since the 1960s, and they're not just shaking pom poms around for show. These women perform grueling dance routines that require up to 15 hours of practice a week — a commitment of time and energy for which they're often underpaid and under appreciated.

The thing that's never changed? The women on the NFL squads have always known how to rock a uniform, whether it's a turtleneck sweater and pleated skirt or a skintight, bedazzled pirate costume.

Here's a closer look at how the NFL's cheerleader uniforms have evolved over the decades.

The NFL's breast cancer awareness campaign has been praised and criticized. It has donated about $15 million to the American Cancer Society, partly through the sale of pink, NFL-branded products — but only a small percentage of money spent on this merchandise actually went to cancer research.

After 2010, there were fewer trend-based fluctuations — though harem pants made a brief appearance on the gridiron.

Houston Texans cheerleaders, 2013.
Getty/Bob Levey

In the past few years, many cheerleaders took a stand against apparently widespread mistreatment of women in the industry. In 2014, several former NFL cheerleaders filed lawsuits saying that they'd been underpaid (sometimes netting just a few bucks an hour) and subject to cruel, sexist treatment.

One former cheerleader wrote in Cosmopolitan that she was pulled from a performance for weighing 127 pounds instead of 122. Some were fined for bringing the wrong pom poms or wearing the wrong clothes to rehearsals. Others were subjected to a humiliating "jiggle test" in which their bodies were scrutinized while they did jumping jacks.